The Mercury program was the first human spaceflight program of the United States, initiated by NASA in 1958. Its primary goal was to send astronauts into space and safely return them to Earth, paving the way for future space exploration. The program successfully launched six crewed missions between 1961 and 1963, with notable astronauts like Alan Shepard and John Glenn. The program's key achievements included the first American in space, Alan Shepard, and the first American to orbit the Earth, John Glenn. The Mercury spacecraft was designed to carry a single astronaut and was crucial in gathering data about human spaceflight, ultimately contributing to the success of later programs like Gemini and Apollo.